I don't think there'll be any changes. I think we're looking for dept where there isn't any. Fact is Capcom has never been known for their compelling narrative, nor characters. They have made some of the greatest games we know we want more from them but Kyrie isn't a particularly profound nor interesting girl. Her character is almost none existent outside of Nero and if she wasn't a singer or Nero a descendant of Sparda they'd be defined by each other rather than what each can offer the screen.
As for her after DMC4, I don't know that she'd change much. Her believes have been confirmed, she met her god's son and she's knocking boots with another descendant, can't imagine her being any happier with her faith.